The Yellowstone River partially re-opened today, but the popular 51-mile stretch that flows through Montana's Paradise Valley remains closed due to a parasite that's killed thousands of mountain whitefish here.

The Yellowstone River in Montana's Paradise Valley, north of Yellowstone Nat'l Park. (Photo Donna Lawson.)

State officials lifted the closure outright downstream of U.S. Highway 89, which covers more than 100 miles of river between Livingston and Laurel. But they extended the closure along a 51-mile stretch of the Yellowstone in the Paradise Valley where thousands of mountain whitefish died in recent weeks.

Fish and wildlife officials are allowing rafting and some other activities to resume on a 26-mile stretch just north of Yellowstone National Park. Fishing remains banned in that area.

Montana officials closed 183 miles of the Yellowstone nearly two weeks ago. The goal of the unprecedented closure was to keep the parasite from spreading, and to lessen stress on fish.

The terrible fish die-off and the businesses hurting over the river closure demonstrate both how fragile the Yellowstone River system is, and just how much the local economy depends on a healthy river. The last thing this river needs is more stressors. Our hearts go out to all the business owners who look to this river for their livelihoods.

With today's welcome news, the affected communities along the Yellowstone can embrace cautious optimism. This challenging episode can be an opportunity to make river conservation -- specifically, protecting the Yellowstone River system -- a higher priority. We've been fortunate that it appears to be a fast-hitting and hopefully a short-duration microscopic invader instead of a more persistent and costly-to-remove foe. When the immediate threat has subsided we need to look ahead to preventing potential future introductions that threaten the health of our rivers and the well-being of our communities.